554 Mr. Williamson on the Limestones 



from the black bass, and evidently connected with the teeth of 

 fish. Attached to a peculiar round body are two teeth (?) 

 about half an inch long, with the two lateral cutting edges 

 finely denticulated : they are separated about ^^jth of an inch at 

 their base, but diverge until their points are nearly half an inch 

 asunder. I only know one ])ortion of a fish to which this sin- 

 gular fossil could belong, and that is, the apex of the upper 

 jaw. In many species of foreign fish are two teeth in that 

 situation which diverge as in our specimen, and this must 

 have been of a similar nature. It may belong to the same 

 species as the long rays*. 



In the roof of the Four-feet mine. Professor Phillipshas been 

 so fortunate as to discover remains of Megalichthys Hibbertii, 

 a fossil which is now apparently diffused through several 

 of the limestones of the coal series : Mr. Mellor has in his 

 possession a beautiful specimen of a lower jaw with a row of 

 five teeth, with several other fiagments. These are generally 

 indistinct and ill defined in their outlines. With the excep- 

 tion of Mr. Mellor's beautiful jaw, the finest specimens of this 

 interesting nnimal have fallen into the possession of Professor 

 Phillipsf, who will doubtless, in his expected paper at the 

 meeting of the British Association, give a detailed account of 

 them, and their affinity with specimens from other districts 

 which I have not had an opportunity of examining. 



The following catalogue comprehends such remains as we 

 have now discovered in and above the third or main limestone : 



PlantcB. — Neiiropteris cordata, Pecopteris, Sphenophyllum, Sphenopteris 

 linearis ?, Cvclopteris, Lepiclodendron Sternbergii, Stigmaria ficoides, Cala- 

 mites decoratus, Calamites nodosus, Asterophyllites. 



Mollusca. — Planorbis, Unio, unknown Bivalve ?. 



Entomostraca. — Cypris, Daphnoi'dea ?. 



Ichthyolites. — PaIa2oniscus (scales and teeth). Teeth, opercular bone, and 

 rays of an unknown species. Megalichthys Hibbertii (scales, lower jaw, 

 teeth, &c.). 



Sect. IX. General Results and Inferences. 



From these detailed descriptions and simple facts, we may 

 draw a few inferences as to the nature of the limestones and the 

 circumstances under which they have been deposited. 



This group of limestones has hitherto, as I before observed, 



• Since the above was written I have discovered a second specimen of 

 this most interesting fossil, closely resembling the one described, with the 

 exception of being rather smaller : it throws no new light upon its nature, 

 except exhibiting a small rounded tooth or process, about -^th of an inch 

 long, fixed between the other two. At the same time I found an opercular 

 bone, probably connected with the same species. 



t Since then I have found a large scale of this animal in the black bass, of 

 a rhomboidal form and closely resembling the scales of the thigh of the 

 American alligator. 



